1. Field of the Invention
The present invention relates to an apparatus for changing the size of a photographing aperture in a camera, for example, from a standard size to a panoramic size (or a half size, etc.) and back to the standard size.
2. Description of Related Art
There are known cameras in which the size of a photographing aperture can be varied from a standard size (24 mm.times.36 mm) to a small size, e.g., a panoramic size (13 mm.times.36 mm), while a film roll is inserted in the camera. To change the photographing aperture size, it is known to provide a pair of light intercepting plates in the vicinity of a photographing aperture which defines a standard size photographing aperture. The pair of light intercepting plates are advanced into the photographing aperture by a predetermined amount to reduce the size of the photographing aperture. When the photographing aperture size is changed back to the standard size, the pair of light intercepting plates are retracted from the photographing aperture. In the known photographing aperture changing apparatus, the pair of light intercepting plates are positioned in the vicinity of the photographing aperture on the side of a photographing lens (i.e., object side) of the camera and are moved into and retracted from the photographing aperture in a linear manner (i.e., the plates are moved in a plane perpendicular to an optical axis of the photographing lens).
In a conventional camera having the above structure, since the pair of light intercepting plates are positioned in the vicinity of the photographing aperture, but on the side of the photographing aperture nearest to the photographing lens, the pair of light intercepting plates and the film plane are further apart from one another than the photographing aperture and the film. As a result, when a picture is taken with the reduced size aperture, a pair of edges of a photographing image on a film are likely to be blurred. The blurred edges correspond to the edges of the light intercepting plates. Furthermore, when a picture is taken with the reduced size aperture, the aperture which is defined by the pair of light intercepting plates sometimes does not correspond to the actual size of the photographing image on a film. Specifically, in the case of an SLR camera to which various types of photographing lenses can be detachably attached, the actual photographing image on a film tends not to correspond to a desired photographing size, since an angle of light rays incident on an image surface varies depending upon the focal length of the photographing lens.